/Engine/Source/Runtime/UMG/Public/Blueprint/SlateBlueprintLibrary.h
Translates absolute coordinate in desktop space of the geometry provided into local viewport coordinates.
static void AbsoluteToViewport ( [UObject](API\Runtime\CoreUObject\UObject\UObject) * WorldContextObject, FVector2D AbsoluteDesktopCoordinate, FVector2D & PixelPosition, FVector2D & ViewportPosition )